Vacuum tube



Sent. 13, 1938.

W. a. TAYLOR VACUUM TUBE f Filed July 2, 1957 Patented Sept. 13, 1938 UNITED STATES PATENT OFFICE VACUUM TUBE Warren G. Taylor, Chicago, Ill. Application July 2, 1997. serial No. 151,690

9 claims. (o1. 25o-27.5)

This invention relates to vacuum tubes and particularly to the construction of the anodes therefor. As is well known, the impedance of a vacuum tube is a function of the distance between the opposing electrode surfaces. Thus, if the anode and cathode are separated by a greater distance under similar grid conditions, the im- I pedance of thetube goes up, while the capacity goes down. It is generally desirable to haveV a low capacitance but for the most purposes it is also desirable to have a lowimpedance.

To attain the above object, the main body of the anode is preferably disposed at a substantial distance from the cathode so that a desired minimum capacitance exists. In order to reduce the impedance, however, I dispose a plurality of wing members on the inside of the anode surface extending toward the cathode. This results in a distortion of the electrostatic eld and tends to divert a substantial portion of the electron stream directly to these wing members.

These wing members are preferably of tantalum and are so designed with regard to thickness and operating conditions that during the normal operation of the tube, the tantalum wings are heated at least to a dull red heat. Under such conditions, tantalum has the property of acting as a getter and cleans up whatever gases and vapors may be present'within the tube. Preferably, the anode proper may begmade of graphite which, as an anode, is particularly desirable. Because of black body radiation, a carbon electrode may be run much more efficiently than other electrodes. The most serious disadvantage up to date with graphite electrodes or any other form of carbon, has been the difficulty of complete removal of absorbed gases. It frequently happens that in the course of time, a graphite electrode, particularly under severe overload, will give up some gas and render the tube gassy. Of course, the usual getter will absorb a certain amount of gas, but, in many instances the evolution of gas from the carbon electrode 4 far exceeds the gettering ability of the substance generally used. With tantalum, however, it is possible to absorb a substantial quantity of gas and the absorption is most efficient when the tantalum is just below white heat. By proper 50 design of the tube, it is possible to have such operating conditions under severe overload when the graphite anode is most likely to evolve gas. This gettering action is preferably supplemental to the usual getter, although, of course, if enough tantalum be provided in the form of wings, the

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usual getter capsule may be reduced in quantity or even eliminated. j

Referring to the drawing:

Figure'l is an elevation partly in section of a tube embodied in this invention.

Figure 2 is a section along line 2 2 of Figure 1.

Figure 3 is a detail of one form of tantalum Wing.

-The tube comprises an envelope IU of glass or any other material, having reentrant stems I I and I2 at opposite ends terminating in presses I3- and I4. Sealed in press I3 are a plurality of wires including a pair of filament leads I6. Supported by leads I6 is an electrode structure comprising a pair of spaced insulators I8 and I9 each in the shape of a cross, although any other shape may be used if desired. Passing upwardly through themid-portion of insulator I8 is a lament 28, the top of which 2| is maintained taut by a spring 22 pressing against the outer surface of insulator I9. Inasmuch as this construction is well known, further details in regard thereto are unnecessary. DisposedV aroundA filament 2U and, it is understood, of course, Ythat an indirectly heated cathode may be used if necessary, is a grid 23 held by grid posts 24 and 25. The grid.y posts 24 and 25 pass through opposed arms of insulators I8 and I9. The remaining arms of insulators I8 and I9 have a pair of rods 21 and 28passing therethrough which support the anode. The bottom of rods 2l and 28 are preferably enlarged at 29 and 39 to prevent them from being pulled up through insulator I8. Immediately above insulator I8 and around each rod are sleeves 3| and 32 which act to space an anode 35 above insulator I8. Additional sleeves 36 and BIfabove anode 35 and below insulator I9 are also provided for spacing purposes. Above insulator I9, sleeves 38 and 39 are provided. A pair of support wires 40 and 4I sealed in press I4 are welded to the free upper ends of wire rods 21 and 28 to maintain 'the entire assembly intact. The usual getter pole 42 supported by a wire 43 may be disposed in any suitable manner as toy support rod 4I. Both support rods 4B and 4I are at anode potentialV andy are connected to an anode terminal 45 sealed on the outside of the tube. The lament leads I6 going through the bottom press I3 may be connected to suitable prongs 46 and 41 disposed in a base 48. The grid posts are prevented from moving vertically by means of straps 49 Welded to the posts above and below insulator I8 and a connection to the grid is made by wire 5U and lead 5I welded to a lead 52 sealed into the envelope. A metal cap 53 cemented to the glass tube serves as a connection to the grid.

Referring to the anode in greater detail, this electrode is preferably of graphite although it is to be understood, that this invention is not limited thereto. The anode proper may be of any suitable metal or material, but in the preferred form, graphite is used. As shown, the anode has its inner surface 60 nished off to provide a flattened cylindrical cross-section.' As clearly shown in Figure 2, graphite has substantial thickness and is provided with a plurality of steps 6| and 62 where the support rods 21 and 28 pass through. As clearly shown, these support rods pass through the thickest portion of the anodeso that ample mechanical strength is assured.

Disposed along the inside surface and preferably along the flattened portion 64 thereof, is a. tantalum member 65 comprising a flat back member 66 having a pair of wing extensions 61 and 68 extending at right angles thereof. Back 66 has the upper and lower ends 69 and 10 bent along lines 1I and 12 just beyond the ends of wings 61 and 68; Beyond lines 1| and 12, the ends are bent parallel to Aeach other and at right angles to back 66 for a short distance and from the mid-portion of each end small fastening ears and 16 are provided. As clearly evident in Figure 2 of the drawing, back 66 is adapted to fit against the inside surface ofY anode 35, while the two wings 61 and 68 extend outwardly toward grid 23. The bent flanged ends 69 and 10 fit over the top and bottom surfaces 11 and 18 of anode 35 while ears 15 and 16 are adapted to be disposed against the sleeves on both sides of the anode. By spot-welding ears 15 and 16 to the corresponding sleeves the entire wing construction is rigidly maintained in position.

While the member shown in Figure 3 is provided with two wings, it is understood, of course, that as many wings may be provided as may be desired. During the operation of the tube, the plurality of bends at each end of back section 66 provide hinges which yield and permit the wings and the back section 66 to expand when heated. In order to maintain the characteristics of the tube at a constant value, itis important that buckling of the wings be prevented and a constant distance between the wings and grid be maintained. By the construction disclosed herein, heating of the anode and particularly of the wings, merely results in elongation and has no effect on the cross-sectional relationship of the electrodes. During the operation of the tube, wings 61 and 68 become hot enough so that a decided gettering action results, While at the same time the electron path is shortened sufficiently to reduce the impedance of the tube.

By the term, normal operating conditions, as hereinafter used in the claims, is meant, not only the normal load for which a Ytube is rated, but

also overloads which are customarily encountered' especially during coagulation, the currents may rise to high values and for short periods of time may result in severe overloads. Such conditions are normal for this class of service. Hence, any tube which is used in a device of this character must withstand severe overloads as part of its normal use. The tube herein disclosed is useful for such service and has been found to be unusually satisfactory.

What is claimed is:

1. A vacuum tube comprising an evacuated receptacle having a cathode and a carbon anode and tantalum vanes electrically connected to said anode and extending toward said cathode and being so proportioned that during normal operating conditions said vanes are heated to at least dull red.

2. A vacuum tube comprising an evacuated receptacle having a cathode and a carbon anode surrounding the cathode, said anode having a plurality of tantalum vanes extending from the inside surface thereof toward said cathode and being adapted under normal operating conditions to be heated at least to a dull red.

3. .A vacuum tube comprising an evacuated receptacle having a cathode and an anode therein and a tantalum member carried by said anode having wing portions extending edgewise toward said cathode and during normal operation of the tube being at least at red heat, and means including at least one hinge portion on said tantalum member for preventing buckling of the member due to heat.

4. A vacuum tube comprising an evacuated receptacle having a cathode and an anode surrounding the same, and a tantalum member disposed on the inside surface of said anode and having wings extending toward said cathode edgewise and during the normal operation of the tube being adapted to operate at least at a red heat and means for supporting said tantalum member on said anode whereby said wings may expand when heated without substantially changing their distance from said cathode.

5. The tube of claim 4 wherein said supporting means comprises a bent member at each end of the tantalum member adapted to take up the expansion of said tantalum member under heat.

6. The tube of claim 4 wherein said anode is of graphite.

'7. A vacuum tube comprising an evacuated receptacle having a cathode, a grid surrounding said cathode and ananode surrounding said grid, and one or more tantalum vanes extending from the inside surface of said anode edgewise toward said cathode and spaced from said cathode at such a distance that under normal operating tube conditions such vanes glow at least at red heat.

8. The tube of claim 7 wherein said anode is of graphite. Y

' 9. The tube of claim 7 wherein said tantalum members are mounted at their ends at the ends of the anode, said mounting ends being bent to take'up the expansion of said tantalum under heat.

WARREN G. TAYLOR. 

